Auto merge of #81761 - m-ou-se:rollup-xp7v07n, r=m-ou-se

Rollup of 9 pull requests

Successful merges:

 - #74304 (Stabilize the Wake trait)
 - #79805 (Rename Iterator::fold_first to reduce and stabilize it)
 - #81556 (introduce future-compatibility warning for forbidden lint groups)
 - #81645 (Add lint for `panic!(123)` which is not accepted in Rust 2021.)
 - #81710 (OsStr eq_ignore_ascii_case takes arg by value)
 - #81711 (add #[inline] to all the public IpAddr functions)
 - #81725 (Move test to be with the others)
 - #81727 (Revert stabilizing integer::BITS.)
 - #81745 (Stabilize poison API of Once, rename poisoned())

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_ast/src/lib.rs

@@ -14,7 +14,6 @@
 #![feature(const_fn_transmute)]
 #![feature(const_panic)]
 #![feature(crate_visibility_modifier)]
-#![feature(iterator_fold_self)]
 #![feature(label_break_value)]
 #![feature(nll)]
 #![feature(or_patterns)]

compiler/rustc_ast/src/mut_visit.rs

@@ -28,7 +28,7 @@ pub trait ExpectOne<A: Array> {
 
 impl<A: Array> ExpectOne<A> for SmallVec<A> {
     fn expect_one(self, err: &'static str) -> A::Item {
-        assert!(self.len() == 1, err);
+        assert!(self.len() == 1, "{}", err);
         self.into_iter().next().unwrap()
     }
 }